1. Field of the Invention
This invention relates to a laminating method using ultrasonic welding where at least three thermoplastic resin plates (hereinafter referred to as "plastic plate") are superposed to form a laminate, such as, a frame of a chemical analytical slide used for supporting a chemical analytical film.
2. Description of the Prior Art
Heretofore, in a conventional manner of welding plastic plates by utilizing frictional heat generated by ultrasonic vibration in the plastic plates, projections called energy directors have been provided (hereinafter referred to as "energy concentrating bodies") for concentrating ultrasonic vibration energy at arbitrary points on the plastic plates. In this method, the manufacturing cost was increased because of the need to furnish plastic sheet materials with the energy concentrating bodies. For example, for forming projections on the plastic sheet by embossing, embossing equipment and additional labor were required. Particularly, for making a laminate by superimposing three or more plastic plates one on another the manufacturing cost was considerably increased because two or more plastic plates have to be furnished with the projections. In addition, forming such projections causes the accuracy in of the thickness and flatness of the plates to be decreased.
Therefore, it was desired to develop a method for ultrasonic welding capable of bonding three or more plastic plates without forming energy concentrating bodies on the sheet material prior to bonding and capable of securing flatness.